Rates of Reaction of Dissolved Oxygen With Scavengers in Sweet and Sour Brines

Rates of reaction of dissolved oxygen with H₂S were measured in a laboratory apparatus using a polarographic type instrument for the measurement of oxygen concentrations. Results show that oxidation occurs only at high pH in the absence of catalytic species. The reaction is catalyzed by transition metal ions in the order Ni⁺⁺>Co⁺⁺>Mn⁺⁺>Cu⁺⁺>Fe⁺⁺. In all cases, the reaction rate increases with pH and is at first complex but becomes zero-order with respect to oxygen after a brief induction period. Some natural waters contain sufficient catalysts that additional amounts are not required for scavenging O₂ with SO₂ or Na₂SO₃. Sour waters cannot be scavenged with SO₂ or Na₂SO₃ because of ineffectiveness of catalysts.